1. Field of Art
The disclosure generally relates to the field of off-line power supplies, and specifically to providing power for an off-line switcher of an off-line power supply.
2. Description of the Related Art
Off-line power supplies typically use an auxiliary power supply for the control circuitry and the power switchers. Isolated power supplies obtain the auxiliary power from auxiliary transformer windings. However, non-isolated power supplies, where transformers are not used, having a transformer for supplying the auxiliary power is not cost effective.
Typically, non-isolated power supplies use additional circuitry to provide power to the control circuitry and the power switchers. For instance, some off-line power supplies may use a high voltage linear regulator to provide the auxiliary power. Alternatively, other off-line power supplies may use an output voltage bootstrap diode. In many cases, these additional circuitry may use high voltage processes (e.g., 600 V or higher) and/or may be inefficient.
Thus, it would be advantageous to be able to efficiently provide auxiliary power for the control circuitry and the power switchers of an off-line power supply without using a high voltage process.